1. Field of the Invention
The present invention concerns data input and is particularly, though not exclusively, concerned with devices which have a very limited number of keys.
2. Description of Related Art
With the increasing miniaturisation of electronic devices it has become increasingly difficult to provide full keyboards in the available space.
A typical example of such a device would be a mobile phone. Another example is the Home-Fax (TM) manufactured by Canon Inc which can store names and associated phone numbers in a “phonebook” memory. In such a device entering text and numbers is a relatively complex operation because of the limited key-set available.
Thus many small devices without a keyboard would benefit from the ability to enter text and digits by voice. However, the replacement of key operated entry of names and numbers by a speech recognition interface raises a number of difficulties which are made worse when the devices are intended to be both small and relatively inexpensive.
Firstly the audio quality on such devices may be low. There are several reasons for this. Obviously in an inexpensive device cost is a limiting factor. Additionally on a mobile phone the background noise may be loud. For example the user could be on a train. Additionally the environment is likely to be different each time the device is used making accurate modelling of the noise characteristics difficult. Where a hands-free microphone is used the distance between the user and the microphone may limit the device's ability to reject background noise. Since the purpose of having a speech interface is to simplify a task that is carried out relatively infrequently it may not be acceptable to require a user to go through a training procedure. Thus another difficulty is that a speaker independent solution may be required. Furthermore, the device may also be used by several users again making a completely speaker independent solution preferable.
Yet another problem of inexpensive devices is that the processing capabilities available on the device may be limited by cost, battery life requirements and other factors such as its physical size. Thus as well as the complexity of the calculations that may be performed as part of the recognition algorithm being limited, the amount of working memory may also be limited as may the amount of pre-calculated data available to the program.
For the above reasons a speech interface for entering small amounts of text on a consumer device is a difficult task and recognition accuracy is likely to be low.